Fast detection of sildenafil in adulterated commer

Authors: J Maria M I Noordin

Publish Date: 2013/10/09

Volume: 115, Issue: 2, Pages: 1907-1914

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Abstract

Adulteration of drugs is a serious issue and can have a great impact on human health It is mainly done with the intention of boosting the effects of products For many years the enforcement officers in Malaysia have had difficulty deciding whether some products should be confiscated as they have not been able to produce fast reliable evidence of adulteration For that reason we explored the use of differential scanning calorimetry DSC as a potential fast detection method of commercial products marketed in Malaysia that may be adulterated We confirmed the outcomes qualitatively with high pressure liquid chromatography DSC was set at a heating rate of 10 °C min−1 and within a temperature range of 100–250 °C with nitrogen as a purge gas at a flow rate of 20 mL min−1 to analyse a sildenafil reference standard RS sildenafil tablets and sildenafil adulterated commercial products Four sildenafil adulterated commercial products were analysed Since the melting point of sildenafil in the mixture tended to shift the presence of sildenafil in three of these adulterated commercial products was confirmed using the spiking method and was reanalysed using DSC The reanalysed results indicated that the enthalphy of fusion ∆H and the resolution peak of sildenafil increased accordingly depending upon the amount of spiked sildenafil RS Apart from these results the DSC curves also showed different patterns for sildenafil RS and the mixtures Therefore we concluded that DSC can potentially be used to detect sildenafil in adulterated commercial productsCurrently there are many commercial products such as herbal preparations health foods and dietary supplements available in the market Most of these preparations seem to be popular among people who believe that products sourced from nature may give better health outcomes without any serious side effects as compared to modern pharmaceutical preparations 1 They also believe dietary supplements are necessary as an additional element required by the body to enhance body functions and healthUnfortunately these were only assumptions that natural products are safe A number of studies done proved that these herbal preparations health foods and dietary supplements were adulterated by other active pharmaceutical ingredients and synthetic drugs such as antiobesity and sex stimulant agent 2 3 4Adulteration of drugs is an illegal practice since it may be dangerous for the health of consumers as the ingredients and the dosage of drugs are unknown It may exacerbate conditions in people who already have an existing illness and also may cause drug–drug interactions in people who are taking pharmaceutical drugs concurrently The Malaysian laws on poisons and sale of drugs 5 are gazetted to convict peoples who offend these laws to protect the Malaysian society from becoming victims of irresponsible personsMost of the traditional medicines and dietary supplements available in the Malaysia market are imported from other countries either by legal or illegal channel Some of them are being manufactured locally Enforcement officers can raid any premises that are suspected of selling or manufacturing adulterated products and seize any suspected products found there At the custom point of entry the enforcement officers need to approve and ensure that all imported drugs comply with the Malaysian Drug Control Authority requirement before being released to the market One of the requirements is that any unregistered or registered traditional or dietary supplement products which consist of any undeclared poisons or substances that may be harmful to consumers should be seized Under section 4 regulation 3 of Sales of Drug Act 1952 it clearly stated that the owner of premises consignor consignee or agent of the owner of products seized may redeem their product after 48 h if it has been confirmed that seized products are free from adulterationThrough our literature search we found studies using differential scanning calorimetry DSC to detect drug in pharmaceutical products 6 as well as to analyse the stability of active ingredients in formulations 7 8 DSC method is also used to detect adulteration in foods materials such as honey to ensure its authenticity 9 The thermal behaviour of pure honey and pure syrups were determined and any differences of the thermal peak due to adulteration was detected and studied In addition DSC technique had also been used in other adulteration studies such as detection of adulteration in olive and virgin coconut oils 10 11 and also detection of water adulteration in butter 12 However we could not find any article on the use of DSC in adulteration of pharmaceutical products In this study DSC will be used as a fast method of detecting adulteration of sildenafil in commercial product samples so that decisions on confiscation of adulterated commercial product can be made within 48 h A qualitative high pressure liquid chromatography HPLC analysis will also be carried out on the same samples for comparisonReference standard of sildenafil citrate Sildenafil RS was purchased from Sigma Aldrich USA Lactose monohydrate was purchased from Aplab Saintifik Malaysia whilst commercial products that were suspected of adulteration were obtained through the Malaysian National Pharmaceutical Control Bureau NPCB

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